feat: add pkg-config find libs

[minhanghuang]

add pkg_check_modules() find lib

example

...
find_package(PkgConfig REQUIRED) # Ubuntu: sudo apt install pkg-config; macOS: brew install pkg-config
pkg_check_modules(Civetweb REQUIRED civetweb)
pkg_check_modules(Civetweb-cpp REQUIRED civetweb-cpp)
include_directories(
  ${Civetweb_INCLUDE_DIRS} # new, /usr/local/include
  ${Civetweb-cpp_INCLUDE_DIRS} # new, /usr/local/include 
)

link_directories(
  ${Civetweb_LIBRARY_DIRS} # new , /usr/local/lib 
  ${Civetweb-cpp_LIBRARY_DIRS} # new, /usr/local/lib 
)

target_link_libraries(${TARGET_NAME}
  ${Civetweb_LIBRARIES} # new, civetweb 
  ${Civetweb-cpp_LIBRARIES} # new, civetweb-cpp
)
...